46 lines
1.2 KiB
Python
46 lines
1.2 KiB
Python
#!/usr/bin/env python
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from decimal import Decimal
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from agate.aggregations.base import Aggregation
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from agate.data_types import Number, Text
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from agate.exceptions import DataTypeError
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class MaxLength(Aggregation):
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"""
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Find the length of the longest string in a column.
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Note: On Python 2.7 this function may miscalcuate the length of unicode
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strings that contain "wide characters". For details see this StackOverflow
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answer: http://stackoverflow.com/a/35462951
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:param column_name:
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The name of a column containing :class:`.Text` data.
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"""
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def __init__(self, column_name):
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self._column_name = column_name
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def get_aggregate_data_type(self, table):
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return Number()
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def validate(self, table):
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column = table.columns[self._column_name]
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if not isinstance(column.data_type, Text):
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raise DataTypeError('MaxLength can only be applied to columns containing Text data.')
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def run(self, table):
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"""
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:returns:
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:class:`int`.
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"""
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column = table.columns[self._column_name]
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lens = [len(d) for d in column.values_without_nulls()]
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if not lens:
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return Decimal('0')
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return Decimal(max(lens))
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